1. Field of the Invention
The present invention relates to a disc clamping device, in which various media discs such as, for example, CDs, DVDs, MDs, CD-ROMs and the like are placed on a turntable and held in a predetermined position by a plurality of clamp bodies protruding in a radial direction outwardly from a center engagement body.
2. Related Art
Generally, when a disc is mounted to a disc clamping device, the disc is easily held in a center position by the clamping device. In a conventional self-clamping device as shown in FIG. 6, a plurality of nail-shaped (circular shaped) clamp bodies 3 are provided so that a tip operating portion 3a of the clamp body 3 can be retracted or extended from an outer peripheral surface 2a of an engagement body 2 through which a center hole 1a of a disc 1 is passes through.
When the center hole 1a of the disc 1 is passed through the engagement body 2, a bottom edge portion 1b of the disc 1 in an axial direction abuts against a displacing inclined surface 3b provided on the upper surface of the tip operating portion 3a of the clamp body 3, since the displacing inclined surface 3b protrudes from the engagement body 2.
When the disc 1 is depressed downward in an axial direction, the clamp body 3 is pushed back into the inside of the engagement body 2 by a generated force of depression in a radial direction.
As shown in FIG. 7, when the disc 1 is mounted in a final fixed location with respect to the engagement body 2, the tip operating portion 3a of the clamp body 3 is pressed in an outward radial direction by a coil spring (not shown), and a holding inclined surface 3c provided on an under surface of the tip operating portion 3a of the clamp body 3 presses against an upper edge portion 1c of the center hole 1a of the disc 1. In this way, the disc 1 is held and fixed by a downward force in an axial direction which is generated by the clamp body 3.
In the conventional self-clamping device having a clamp body 3, when the clamp body""s height dimension is reduced in order to make the clamping device thinner, the disc cannot be properly clamped. As shown in FIG. 7, the axial height position A of a top portion 3d, which is formed by a border portion between the displacing inclined surface 3b in the upper surface of the tip operating portion 3a and the holding inclined surface 3c in the under surface of the tip operating portion 3a of the clamp body 3, is set a little higher than the thickness H of the disc 1 in the finally fixed location.
Accordingly, in order to make the height position B of the uppermost surface 3e of the clamp body 3 lower, it is necessary, for example, to make the thickness or the dimension between A and B thinner.
However, when the dimension or the spacing between A and B is made thinner, the angle of the displacing inclined surface 3b becomes more gradual. Consequently the component of a force to make the clamp body 3 to move in a radial direction becomes smaller and the clamp body 3 will not move easily and smoothly. As a result, disc 1 has to be depressed strongly against the displacing inclined surface 3b, which leads to unsatisfactory performance.
Alternatively, a guiding portion for the center hole 1a of the disc 1 can be provided on the top surface of the engagement body 2 to make the positioning operation perform smoothly. However, incorporating the guiding portion makes the entire clamping device thicker and the height of the device still cannot be lowered.
The present invention provides a thinner disc clamping that is able to clamp and hold a disk in a center position with ease.
According to one embodiment of the present invention, a tip operating portion of a clamp body moves downward by a depressed disc. An entry guide portion provided in an engagement body is exposed and the disc is guided along the entry guide portion to a center location. Thus, the disc is properly centered without a guiding operation by the clamp body.
Also, when the disc has been fully clamped, the tip operating portion of the clamp body is moves upward by an upward reaction force by the disc, and the disc is clamped in a fixed position as the tip operating portion of the clamp body presses the upper surface of the disc.
Accordingly, even if the axial width of the clamp body is smaller than the thickness of the disc, the clamping of the disc is performed without any problems. As the axial dimension of the clamp body is made smaller, the entire height of the clamping device is not increased even though the device includes the entry guide portion.
In accordance with an embodiment of the present invention, when the disc is not being clamped, or when the disc has been clamped and the disc has pushed up the clamp body in an upward position, the uppermost surface of the clamp body is positioned so as to be generally the same height of an uppermost surface of the entry guide portion of the engagement body. Thus the height dimension does not increase and the disc is clamped without any problems.
In addition, in accordance with an embodiment of the present invention, a drive source is a motor, a turntable is fixed to a rotor case which rotates with a rotor shaft of the motor, and clamp bodies are held by the rotor case in such a manner that each of the clamp bodies is movable in a radial direction. Thus, the disc clamping device is suitably integrated with a motor.
Other features and advantages of the invention will be apparent from the following detailed description.